A decolorizable ink in which a leuco dye and a color developing agent are dissolved in an organic solvent is being developed as an ink for inkjet recording. An image formed on a paper medium using such a decolorizable ink can be erased (decolorized) by heating. However, when an oil-based ink containing an organic solvent is used, there is a possibility that by applying the ink again to the paper medium after decolorization, the decolorized ink may develop the color again.
From the viewpoint of reduction in volatile organic compounds (VOC), it is desired to use a water-based ink containing a water-based solvent such as water, however, such a water-based ink is liable to cause curling of a paper medium. When a coverage is increased, curling of a paper medium is particularly prominent. A water-based ink having a high water content is liable to dry, and when the ink is used for inkjet recording, clogging of inkjet heads is liable to occur.
A decolorizable water-based inkjet ink which dries at an adequate rate and can form an image on a paper medium without causing curling is not obtained yet.